Optics of carbon fiber-reinforced plastics – A theoretical and an experimental study

• Published in: Journal of quantitative spectroscopy & radiative transfer Vol. 180; pp. 70 - 76
• Main Authors: Hohmann, Ansgar, ElMaklizi, Ahmed, Foschum, Florian, Voit, Florian, Bergmann, Florian, Simon, Emanuel, Reitzle, Dominik, Kienle, Alwin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-09-2016
• Subjects: Carbon fiber; Carbon fiber reinforced plastics; CFRP; Computer simulation; Fibers; Mathematical models; Maxwell's equations; Maxwell׳s equations; Polymers; Radiative transfer; Radiative transfer equation; Reflectance; Refractive index; Radiative transfer equation; Maxwell׳s equations; Refractive index; CFRP; Carbon fiber-reinforced plastics; Carbon fiber
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2016.04.015

Laser processing of carbon fiber-reinforced plastics (CFRP) as well as their design optimization are strongly emerging fields. As the optics of CFRP is still rather unknown, the optical behavior of CFRP was investigated in this study. Different simulation models were implemented to simulate reflectance from CFRP samples as well as distribution and absorption of light within these samples. The methods include an analytical solution of Maxwell׳s equations and Monte Carlo solutions of the radiative transfer theory. We show that strong inaccurracies occur, if light propagation in CFRP is modeled using the radiative transfer theory. Therefore, the solution of Maxwell׳s equations is the method of choice for calculation of light propagation in CFRP. Furthermore, measurements of the reflectance of light from CFRP were performed and compared to the simulations for investigation of the optical behavior. Information on the refractive index of carbon fibers was obtained via goniometric measurements. The amount of reflected light was determined as 6.05±0.38% for light polarized parallel to the fiber direction, while it was 3.65±0.41% for light polarized perpendicular to the fiber direction in case of laser-processed CFRP.
•The light scattering of CFRP was studied using Maxwell׳s equations and radiative transfer theory.•The simulations were validated by experiments.•Strong inaccuracies occur if light propagation in CFRP structures is modeled with the RTT.•The Bouguer–Lambert–Beer model with μa=4πfVIm(ncyl)/λ cannot be used in CFRP samples.•Reflectance values were determined and information on the refractive index was inferred.